I always find let's call it a day in that usual form but I am curious to see if it is possible to use it in other grammatical forms. For example, can I use can/do/should or any other form for that matter?
Sometimes you want to make the suggestion but in a more tentative way. What I am concerned with is the prospect of deviating from the common form. More than one example would help me better see how much wiggle room there is in steering away from the standard form.
None of the dictionaries I have checked answer my question.